Rotary pump



Sept. 15, 1964 E. E. SMITH 3,148,626

ROTARY PUMP Filed May 14, 1962 4 Sheets-Sheet l I3 rx mxmxmxmxmxmx 1m Fig. 7

INVENTOR. Edwin E. Smith Y 071% zmia Attorneys Sept. 15, 1964 E. E. SMITH 3,148,626

ROTARY PUMP Filed May 14, 1962 4 Sheets-Sheet 2 f 2 I? A I7 29 p'- I6 39 1 39 F I g 2 INVENTOR. Edwin E. Smith Attorneys E. E. SMITH ROTARY PUMP Sept. 15, 1964 4 Sheets-Sheet 3 Filed May 14, 1962 rum! INVENTOR.

Edwin E. Smith BY Attorneys Sept. 15, 1964 E. E. SMITH ROTARY PUMP Filed May 14, 1962 VOL. FLOW RATE CFM VACUUM "Hq Fig. 8

VOL. FLOW RATE CFM H ORSEPOWER 4 Sheets-Sheet 4 I000 I400 I800 RPM Fig. I0

" Vacuum RPM jl l INVENTOR.

BY Edwin E. Sgt;

Attorneys United States Patent 3,148,626 ROTARY PUMP Edwin E. Smith, Santa Clara, Calif., assignor to Fluid Dynamics Corp, Santa Clara, Calif., a corporation of California Filed May 14, 1962, Ser. No. 194,314 13 Claims. (till. 103-131) This invention relates to a rotary pump and more particulary to a rotary pump of the type which has a pair of pumping chambers.

At the present time there is a need for a pump which can be utilized as a compressor or vacuum pump and which can be produced at relatively low cost.

In general, it is an object of the present invention to provide a rotary pump which is particularly adapted for use as a compressor or a vacuum pump.

Another object of the invention is to provide a rotary pump of the above character which also can be utilized for pumping liquids.

Another object of the invention is to provide a rotary pump of the above character which is very simple in construction and is relatively inexpensive to manufacture.

Another object of the invention is to provide a rotary pump of the above character which does not require a timing plate.

Another object of the invention is to provide any rotary pump of the above character in which a grease seal can be utilized.

Another object of the invention is to provide a rotary pump of the above character which runs smoothly at relatively high speeds.

Additional objects and features of the invention will appear from the following description in which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings.

Referring to the drawings:

FIGURE 1 is a side elevational view of a rotary pump incorporating my invention.

FIGURE 2 is a cross-sectional view taken along the line 2-2 of FIGURE 1.

FIGURE 3 is a front elevational View looking along the line 3-3 of FIGURE 1.

FIGURE 4 is a cross-sectional view taken along the line 44 of FIGURE 3.

FIGURE 5 is a cross-sectional view taken along the line 55 of FIGURE 4.

FIGURE 6 is a partial view similar to FIGURE 5 showing another embodiment of my pump utilizing sprocket wheels and a chain for timing means.

FIGURE 7 is a partial view also similar to FIGURE 5 showing the use of timing pulleys and notched V-belts for timing means.

FIGURE 8 is a chart showing the flow rate versus vacuum in inches of mercury produced at a constant r.p.m. with a pump incorporating my invention.

FIGURE 9 is a chart showing the flow rate versus speed at a constant vacuum of the same pump.

FIGURE 10 is a chart showing the horsepower versus rpm. for the same pump.

In general, my rotary pump consists of a casing which has inner and outer concentric cylinder walls defining the working space. The casing is formed with inlet and outlet openings leading into and out of the working space. Partition means is provided in the working space extending between the inner and outer cylinder walls and serves to separate the inlet and outlet openings. A cylindrical piston is disposed in the working space and forms two pumping chambers within the working space. Means is provided for imparting circular gyratory movement to the piston in the working space. The piston is formed with a longitudinal slot which permits such movement 3,148,626 Patented Sept. 15, 1964 about the partition means. The means for imparting gyratory movement includes a pair of eccentric shafts rotatably mounted in the piston and the casing and extending longitudinally through the piston. Means is provided for interconnecting the two shafts so that they and the piston operate in a timed relationship. One of the shafts extends out of the casing so that it can be used for a drive shaft. counterweight means is connected to the shaft for balancing the eccentric shafts.

As shown in the drawings, my rotary pump consists of a casing 11. The casing 11 is comprised of an inner cylinder 12 and an outer cylinder 13. The cylinders 12 and 13 are held in a predetermined relationship with respect to each other by front and rear substantially circular end plates 14 and 16, respectively, and which are held together by a plurality of circumferentailly spaced draw bolts 17. It will be noted that the end plates 14 and 16 are provided with annular grooves 13 and 19 which receive the ends of the cylinders 12 and 13. The end plates 14 and 16 are provided with feet 20 which support the pump as shown in the drawings.

The inner and outer cylinders 12 and 13 provide innner and outer concentric cylinder walls 21 and 22 which, in conjunction with the end plates 14 and 16, provide an annular working space 23. The inlet to the working space 23 is provided by a centrally disposed threaded opening 26 in the end plate 14 which opens into the cylindrical space 27 within the inner cylinder 12 and communicates with a plurality of longitudinally spaced intake ports 28 in the cylinder 12 and which open into the annular working space 23. A threaded outlet opening 29 is also provided in the front end wall 14 which is adjacent the lower extremity of the working space 23 for a purpose hereinafter described and which also communicates with the working space 23.

Partition means is provided in the working space 23 which extends between the inner and outer cylinder walls 21 and 22 and serves to separate the inlet and outlet openings and consists of a divider 31 extending longitudinally between the inner and outer cylinders 12 and 13.

A cylindrical piston 34 is disposed in the working space and forms two pumping chambers A and B within the annular working space 23. As can be seen particularly from FIGURE 2, the piston has a substantial wall thickness to provide inner and outer cylinder walls 36 and 37 which cooperate with the inner and outer cylinder walls 21 and 22 of the casing to form the pumping chambers A and B. In order to reduce the weight of the piston, it is desirable that the piston be formed of a suitable light material. such as cast aluminum. The piston is also provided with a plurality of recesses 39 to also reduce the weight of the piston. The piston is formed with a slot 41 which extends longitudinally thereof that permits circular gyratory movement of the piston 34 about the divider 31 as hereinafter described.

Means is provided for imparting circular gyratory movement of the piston 34 in the working space and consists of a pair of eccentric shafts 46 and 47 which are rotatably mounted in the end plates 14 and 16. The shafts 46 and 47 are also rotatably mounted in diametrically opposite sides of the piston 34 and extend through the piston. As shown, the shaft 46 extends out of the front end plate 14 and is used for the drive shaft.

The shafts 46 and 47 are rotatably mounted in the end plates 14 and 16 in a suitable manner such as by the use of needle bearing assemblies 48. Three of the bearings 43 are sealed by suitable means such as Chicago Rawhide Type 7410 seals 49. The other bearing 48 provided for the shaft 47 in the front end plate 14 is completely sealed by a cap 50. The shafts 46 and 47 are provided with eccentric portions 46a and 47a which are rotatably mounted within the piston 34 by suitable means 3 such as needle bearings 51. From the construction described, it can be seen that the shafts 46 and 47 extend longitudinally of the piston 34 and are positioned on diametrically opposite sides of the piston.

Means is provided for operating the shafts 46 and 47 and the piston 34 in a timed relationship. This timing means consists of a pair of substantially semi-circular counterweights 56 and 57 which are releasably secured to the ends of the shafts 46 and 47 which extend through the rear end plate 16 by suitable means such as set screws 53. As will be apparent from FIGURES 4 and 5, the counterweights 56 and 57 are normally secured to the shafts in such a relationship that they are 180 out of phase with the eccentric portions 46a and 47a of the shaft to provide a counterbalance for these eccentric portions and the piston. A timing line 61 interconnects the counterweights 56 and 57 and is pivotally connected to each of the counterweights by a pin 62 which is mounted off-center in the counterweight in a suitable manner such as by means of a press fit. The connections for the links can be located at any angular position on the counterweights in relation to the eccentric portions of the shafts except a position which is parallel to a line which passes through the centers of the two shafts 46 and 47. Preferably, it is desirable to make the connection to the counterweights at an angle of approximately 45 to 90". For example, in the embodiment shown, I have used an angle of approximately 80. A needle bearing 63 is mounted on the pin 62 and carries the associated end of the timing link 61. The timing link is retained on the hearing by means of a washer 64 and a snap ring 66. It will be noted that the counterweights are formed with portions 56a and 57a to counterbalance the weight of the timing link 61 and its connections to the counterweights. With this arrangement, it can be seen that the shaft 46 is the drive shaft, whereas the shaft 47 is the driven shaft. The timing link 61 serves to positively drive the driven shaft 47 during the portion of the cycle when the eccentric portions of the shafts are in line with a line passing through the centers of the two shafts 4-6 and 47. Thus, the link 61 ensures that the piston will continue to move in the circular gyratory path hereinbefore described. During the cycle, when the link 61 is in line with a line passing through the centers of the two shafts, the piston will provide the driving force for the driven shaft because at this point the eccentric portions of the shafts are approximately 90 out of phase with the line passing through the centerline of the two shafts. Thus, continued circular gyratory movement of the piston is assured.

A protective cover 68 is mounted over the timing link 61 and the counterweights 56 and 57 and is supported by brackets 69 held by the draw bolts 17.

The general operation of a pump of this type in which both of the chambers A and B serve as pumping chambers is well known to those skilled in the art and is described in my copending applications Serial No. 168,407, filed January 24, 1962 and Serial No. 53,970, filed September 6, 1960. One of the primary improvements in my rotary pump is the timing means provided for timing the rotation of the shafts 4-6 and 47 and the circular gyratory movement of the piston 34. As can be seen, the counterweights 56 and 57 are provided on the ends of the shafts. The counterweights are thus able to perform two functions, that is, they serve as counterweights and also they serve as part of the means connecting the shafts 46 and 47 and the piston 34 in a timed relationship. It is readily apparent that although I have provided two counterweights of substantially identical size, if desired, all of the weight could be placed in one of the counterweights and the other counterweight replaced by an arm. Another alternative would be merely to provide arms on both of the shafts 46 and 47 which are connected to the link 61 and then providing a counterweight on an extension d of the shaft 47 extending in front of the front end plate 14.

In the construction shown, it will be noted that the divider 31 has been provided at the bottom of the pump between the suction or intake and the discharge or exhaust outlets so as to provide adequate drainage of the pump. In certain uses of the pump, there is a likelihood that condensation will collect within the pump. Also in certain applications, such as for use with milking machines, it is very possible that milk and even cleaning fluids utilized in cleaning the milk lines may enter the pump. My arrangement with the outlet opening 26 in the lower portion of the working space 23 permits these cleaning fluids and any other liquids collected in the pump to be readily drained from the pump.

Because of this construction, my pump should find many applications where a moderate vacuum is required such as in the food processing industry, processing of chemicals, providing vacuums in hospitals and medical centers. The pump is constructed in such a manner that it can be readily manufactured at low cost by the use of low cost production methods such as by the utilization of die cast parts.

My rotary pump is also useful for such purposes because it can readily pass liquids which may have a tendency to stick in other types of pumps such as vane-type pumps and render them inoperable or inetficient. With this type of rotary pump, such material can go through the pump without effecting the efliciency of the pump.

In FIGURES 8, 9 and 10, I have shown charts giving the performance of one pump incorporating my invention. From FIGURE 8, it can be seen that with my pump, I have been able to draw a vacuum of 28.9 inches of mercury. In FIGURE 9, there is shown a volume of free air which is pumped by the pump at two different inlet conditions, one at zero vacuum and one at 15 inches of vacuum at variable r.p.m. The curves show that this pump has a high efiiciency. FIGURE 10 shows the horsepower required at two different vacuum conditions at difierent r.p.m.

In one embodiment of my pump utilizing grease as a sealant within the pumping chamber, I found that I was able to draw a vacuum of over 28 /2 inches of mercury. The use of a grease seal in this type of pump is possible because of the relatively low surface speed developed between the working parts during operation of the pump. In such an embodiment, the pump is manufactured so that there is a small clearance between the wall 37 of the piston and the wall 22 of the casing and also walls 21 and 36 so that there is a small space between the same during all angles of the cycle. In order to pump fluids or gases at an acceptable efficiency, this space must be sealed and it is for this reason that grease has been utilized. Due to the fact that there is a space between the walls as hereinbefore pointed out, the grease remains on the surfaces and, therefore, is not wiped off. Also, for that reason, the grease need not be replenished except very occasionally. In other types of pumps such as vane pumps, the lubrication must be constantly replenished because the vanes have a tendency to scrape the lubricant off of the side walls of the pump. Because of the constant replacement and because the lubricant is being scraped off of the walls, the exhaust from such a pump must be ventilated to the atmosphere. The discharge from such a pump forms an oil fog which must be disposed of in a suitable manner to avoid any hazardous conditions. With my pump since the grease remains on the cylinder walls, there is no contamination of the exhaust by oil from the pump and, therefore, the exhaust need not be ventilated to the atmosphere. Thus, a pump of my type can be utilized in a room without provision of special means for exhaust.

Although I have described my pump utilizing a grease seal, there are applications when no seal would be required. For example, as described, my copending application Serial No. 168,407, filed January 24, 1962, the piston can be coated with a resilient material which provides its own lubrication.

Although my rotary pump has been shown with the slot 41 of the piston 34 facing downwardly, if desired, the pump can be arranged so that the divider 31 and the slot 41 are disposed in any desired angle.

Two additional embodiments of my rotary pump are shown in FIGURES 6 and 7 and consists of two alternative types of timing means for timing the rotation of the shafts 46 and 47 and the piston 34 relative to each other. Thus, in FIGURE 6 I have shown sprockets 76 and 77 which are secured to the shafts 46 and 47 by set screws 78. The timed relationship between the sprockets 76 and 77 is maintained by a link chain 79 of conventional construction. Counterweights 81 are secured to the sprocket wheels by suitable means such as screws 82. Alternatively, the counterweights can be formed as an integral part of the sprocket wheels.

In FIGURE 7, timing pulleys 86 and 87 are secured to the shafts 46 and 47 by set screws 88. A notched V-type timing belt 89 connects the pulleys and, as shown, is provided with timing teeth 89a which engage the teeth 86a and 87a. of the pulleys. Counterweights 91 are again secured to the pulleys by suitable means such as the screws 92.

It is apparent from the foregoing that I have provided a new and improved rotary pump which particularly lends itself to inexpensive production methods and which eliminates the use of expensive castings and the like.

I claim:

1. In a rotary pump, a casing having inner and outer concentric cylinder walls and front and rear end walls defining a working space, said casing being formed with inlet and outlet openings, partition means in the working space extending between the inner and outer cylinder walls and separating the inlet and outlet openings, a cylindrical piston disposed in said working space and forming two pumping chambers within the working space, means for imparting circular gyratory movement of the piston in the working space, said piston being formed with a longitudinal slot permitting movement of the piston about the partition means, said means for imparting gyratory movement including a pair of shafts rotatably mounted in the front and rear end walls of said casing, said shafts having eccentric portions rotatably mounted in the piston and extending longitudinally through the piston, one of said shafts serving as the drive shaft to provide the sole means for driving the pump, and means interconnecting the two shafts so that they operate in a timed relationship with each other and with the piston as said one shaft is driven.

2. A rotary pump as in claim 1 wherein the means interconnecting the two shafts includes a pair of sprocket Wheels mounted on the shaft, a sprocket chain connecting the two sprocket wheels so that as one sprocket wheel is rotated the other sprocket is rotated.

3. A rotary pump as in claim 1 wherein said means interconnecting the two shafts consists of a pulley mounted on each of the shafts, and a timing belt interconnecting the two pulleys so that as one pulley is rotated the other pulley is rotated.

4. A rotary pump as in claim 1 wherein said casing consists of inner and outer hollow open-ended cylinders, front and rear end plates and means for releasably securing the end plates to the ends of the cylinders so that the cylinders are retained to form said inner and outer concentric walls.

5. A rotary pump as in claim 4 wherein the inlet and outlet ports are formed in the front end wall and wherein the inner cylinder is provided with a plurality of longitudinally spaced intake ports extending through the same adjacent said divider.

6. In a rotary pump, an outer hollow open-ended cylinder, an inner hollow open-ended cylinder, front and rear end plates, means for securing the end plates to the ends of the cylinders to form a casing having an annular working space between the inner and outer cylinders and the front and rear end plates, a divider in the working space extending between the inner and outer cylinders, inlet and outlet openings formed in the casing on opposite sides of the divider and communicating with the annular working space, at least one of the openings being formed in one of the end walls, a cylindrical piston disposed in the working space and forming two pumping chambers within the working space, a pair of shafts rotatably mounted in the front and rear end plates, the shafts having eccentric portions extending longitudinally through the piston and rotatably mounted in the piston, one of the shafts serving as the drive shaft to provide the sole means for driving the pump, and means interconnecting the two shafts so that the two shafts operate in a timed relationship with the piston as said one shaft is rotated.

7. A rotary pump as in claim 6 wherein said means interconnecting the two shafts consists of a pair of arms secured to the shaft, and a timing link pivotally connected to the arms.

8. A rotary pump as in claim 6 wherein the means interconnecting the two shafts consists of a pair of wheellike members, and linkage means for connecting the wheel-like members so that as one is rotated, the other in rotated.

9. A rotary pump as in claim 6 wherein said piston has a substantial radial thickness which is greater than the diameter of the eccentric portions of the shafts and wherein the piston is provided with a plurality of recesses spaced circumferentially of the piston to reduce the weight of the same.

10. In a rotary pump, an outer hollow open-ended cylinder, an inner hollow open-ended cylinder, front and rear end plates, means for securing the end plates to the ends of the cylinders to form a casing having an annular working space between the inner and outer cylinders and the front and rear end plates, a divider in the working space extending between the inner and outer cylinders, inlet and outlet openings formed in the casing on opposite sides of the divider and communicating with the annular working space, a plurality of openings formed in the inner cylinder adjacent one side of the divider, one of said inlet and outlet openings being formed in one of said end plates and communicating with said openings in said inner cylinder, a cylindrical piston disposed in the working space and forming two pumping chambers within the working space, a pair of shafts rotatably mounted in the front and rear end plates, the shafts having eccentric portions extending longitudinally through the piston and rotatably mounted in the piston, one of the shafts serving as the drive shaft to provide the sole means for driving the pump, and means interconnecting the two shafts so that the two shafts operate in a timed relationship with the piston as said one shaft is rotated.

11. A rotary pump as in claim 10 wherein the eccentric portions of the shaft have a diameter substantially greater than the remaining portions of the shafts.

12. In a rotary pump, a casing having inner and outer concentric cylinder walls and front and rear end walls defining a working space, said casing being formed with inlet and outlet openings, partition means in the working space extending between the inner and outer cylinder walls and separating the inlet and outlet openings, a cylindrical piston disposed in said working space and forming two pumping chambers within the working space, means for imparting circular gyratory movement to the piston in the working space, said piston being formed with a longitudinal slot permitting movement of the piston about the partition means, said means for imparting gyratory movement including a pair of shafts rotatably mounted in the front and rear end walls of said casing, said shafts having eccentric portions rotatably mounted in the piston and extending longitudinally through the piston, one of said shafts serving as a drive shaft to provide the sole means for driving the pump, and means interconnecting the two shafts so that they operate in a timed relationship with each other and with the piston as said one shaft is driven, said means interconnecting the two shafts including a counterweight mounted on each of the shafts and a link connecting the counterweights.

13. In a rotary pump, an outer hollow open-ended cylinder, an inner hollow open-ended cylinder, front and rear end plates, means for securing the end plates to the ends of the cylinders to form a casing having an annular working space between the inner and outer cylinders and the front and rear end plates, a divider in the working space extending between the inner and outer cylinders, inlet and outlet openings formed in the casing on opposite sides of the divider and communicating with the annular Working space, at least one of the openings being formed in one of the end walls, a cylindrical piston disposed in the working space and forming two pumping chambers within the working space, a pair of shafts rotatably mounted in the front and rear end plates, the shafts having eccentric portions extending longitudinally through the piston and rotatably in the piston, one of the shafts serving as the drive shaft to provide the sole means for driving the pump, and means interconnecting the two shafts so that the two shafts operate in a timed relationship with the piston as said one shaft is rotated, said means interconnecting the two shafts consisting of a pair of arms secured to the shafts and a timing link pivotally connected to the arms, said arms being in the form of counterweights to compensate for the eccentric portions of the shaft.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A ROTARY PUMP, A CASING HAVING INNER AND OUTER CONCENTRIC CYLINDER WALLS AND FRONT AND REAR END WALLS DEFINING A WORKING SPACE, SAID CASING BEING FORMED WITH INLET AND OUTLET OPENINGS, PARTITION MEANS IN THE WORKING SPACE EXTENDING BETWEEN THE INNER AND OUTER CYLINDER WALLS AND SEPARATING THE INLET AND OUTLET OPENINGS, A CYLINDRICAL PISTON DISPOSED IN SAID WORKING SPACE AND FORMING TWO PUMPING CHAMBERS WITHIN THE WORKING SPACE, MEANS FOR IMPARTING CIRCULAR GYRATORY MOVEMENT OF THE PISTON IN THE WORKING SPACE, SAID PISTON BEING FORMED WITH A LONGITUDINAL SLOT PERMITTING MOVEMENT OF THE PISTON ABOUT THE PARTITION MEANS, SAID MEANS FOR IMPARTING GYRATORY MOVEMENT INCLUDING A PAIR OF SHAFTS ROTATABLY MOUNTED IN THE FRONT AND REAR END WALLS OF SAID CASING, SAID SHAFTS HAVING ECCENTRIC PORTIONS ROTATABLY MOUNTED IN THE PISTON AND EXTENDING LONGITUDINALLY THROUGH THE PISTON, ONE OF SAID SHAFTS SERVING AS THE DRIVE SHAFT TO PROVIDE THE SOLE MEANS FOR DRIVING THE PUMP, AND MEANS INTERCONNECTING THE TWO SHAFTS SO THAT THEY OPERATE IN A TIMED RELATIONSHIP WITH EACH OTHER AND WITH THE PISTON AS SAID ONE SHAFT IS DRIVEN. 